1. Field of the Invention
The present invention pertains generally to suction and discharge valves, and more particularly to a valve plate structure having capabilities of reducing noise and vibration generated when suction and discharging valves collide into a valve plate in shutting the same.
2. Description of the Related Art
FIG. 1 shows an enclosed electric compressor of the related art.
As shown in FIG. 1, a crank shaft is fastened to a rotor (not shown) and a stator (not shown) which are electrical components, and one ends of a rotor and a stator are connected to a piston 19. The piston 19 and a cylinder 7 are installed in a cylinder block which is configured with the cylinder 7 to form a single body. Also, the cylinder 7 is coupled with a suction valve 20, a valve plate 22, a discharge valve 26 and a head cover 28 in a bolt-coupling manner.
In a reciprocating compressor of the related art, a crank shaft 3 is rotated at a certain number of revolution by rotating force of the rotor and the stator which are power transmitting components. The rotational motion is converted into reciprocal straight line motion by a sleeve 16 and a connecting rod 17. A piston 19 is fastened to the connecting rod 17, and moves back and forth within the cylinder 7. By back and forth motion of the piston 19, coolant is inhaled through the suction valve 20 and discharged through the discharging valve 26 after being compressed under the high pressure.
FIG. 2A to FIG. 2D show disassembled views of a head cover, the valve plate, the suction valve and the discharging valve.
The valve plate 22 supports the suction valve 20 and the discharging valve 26, and controls the flow of fluid that goes in and comes out of the cylinder 7. The valve plate 22 includes a suction port 221 for intake the fluid and a discharging port 222 for discharging fluid.
The suction valve 20 is positioned between the valve plate 22 and the cylinder 7, and has a suction plate 201 formed at a position corresponding to the suction port 221 of the valve plate 22.
Also, the discharge valve 26 is positioned between the valve plate 22 and the head cover 28, and has a discharging plate 261 formed at a position corresponding to the discharge port 222 of the valve plate 22.
As shown in FIG. 2A, the head cover 28 determines a flow passage for fluid that goes in and comes out of the cylinder, and also includes a mounting surface for mounting a suction muffler 27 at one side thereof and the upper part of the other side is mounted with the valve plate 22. The head cover 28 also includes a suction tube formed at a place corresponding to the suction port 221 of the valve plate 22 and a discharging tube formed at a position corresponding to the discharging port 222.
The head cover 28 configured as above has the upper end to which the valve plate 22 is mounted and the lower end to which the suction valve 20 is mounted. In general, the discharge valve 26 and the suction valve 20 are made of steel and have a thickness of about 1 or 2 t. Meanwhile, the valve plate 22 has a thickness of 3 or 5 t which is thicker than the valves 20 and 26.
The following are the description of the suction, compression and discharge steps of the compressor.
When the piston 19 moves from the top dead center to the bottom dead center, the suction valve 20 opens as the pressure within the cylinder 7 becomes lower than the suction muffler 27. The suction valve 20 remains opened allowing a coolant to be introduced into the cylinder 7 until the pressure within the cylinder 7 becomes the same as the pressure in the suction muffler 27.
Also, when the piston 19 moves from the bottom dead point to the top dead point, internal pressure of the cylinder 7 is successively elevated to compress the coolant. When such internal pressure of the cylinder 7 becomes larger than spring force of the discharging valve 26, the discharge valve 26 is opened to form a passage through which the high pressure of the coolant is discharged from the cylinder.
As shown above, when the rotor revolves for one time the, operation of the suction valve 20 and the discharge valve 26 is initiated and suction and discharge of coolant into and from the cylinder 7 is carried out. When the suction and discharge valves 20 and 26 are closed, the suction and discharge valves 20 and 26 collide into the valve plate 22 thereby generating noise and vibration. The loudness of the collision noise depends on a vibration transmission capability of the valve plate 22.
Also, such vibration is transferred to the valve plate 22 and then transmitted to the whole compressor via a contact area of the valve plate 22 and the bolt that fastens the valve plate 22.
If the vibration transferred to the compressor coincides with the resonant frequency, then severe problems such as noise and fracture may occur, and most of the time it has a large effect on noise generation due to the high frequency component.
In order to reduce such vibration and noise, a cavity is provided at the one portion of the outside of the discharging port and a suction muffler is provided in the suction port.
However, due to the limitation on the volume of the cavity, reducing the whole energy of transmitted noise is limited. Also, it is difficult to reduce noise under a certain reference value.
Further, another disadvantage is that a vibration mode of the valve plate 22 does not absorb impact or collision sound, thereby generating loud noise.